Bestimmung von Wasser in Dichloressigsäure

Water concentrations in dichloroacetic acid in the range of 0<C <1 % (C = percent by weight) can be determined directly by photometry at 1425 nm. The absorbance A at this maximum is described by the function A=1.267×C^0.93 (cell path d=5 cm, correlation coefficient r=0.997). The variation coefficient for water concentrations of ≈0.06% was found to be V=6.5%.     

From microscopic to macroscopic nuclear collective dynamics

We apply smoothing procedures to response functions for isoscalar vibrations. For collective motion, we find a transition from a structured strength distribution to one corresponding to one incoherent, strongly overdamped mode. It is argued that the latter may be interpreted as macroscopic motion exhibiting, to some extent, features of the hydrodynamical model. We discuss the physical origin of this behaviour, in particular its relation to the disappearance of shell structure.Supported in part by the Deutsche Forschungsgemeinschaft     

Crystal structure of 1-hydroxy-1,2,3-benzotriazolium diphenyl phosphate reveals strong NHO and OHO hydrogen bonds

The structure of 1-hydroxy-1,2,3-benzotriazolium diphenyl phosphate (HOBt/DPP) has been investigated by X-ray analysis. The compound crystallizes in the monoclinic space group P2₁/n with Z = 4 and the following lattice parameters: a = 11.711(2), b = 12.727(2) and c = 12.794(3) Å, β = 105.12(2)°, V = 1840.9(6) ų. The structure was solved by direct methods and refined on F² to R values of wR2 = 0.084 and R1 = 0.034 for 1985 observed reflections. HOBt/DPP has an ionic structure with very short OHO and NHO hydrogen bonds linking the different ions. Owing to these hydrogen bonds, infinite screw-shaped chains which are twisted parallel to the y-axis are formed.     

Ein neues Oxogermanat: Li8GeO6 = Li8O2[GeO4]. (Mit einer Bemerkung über Li8SiO6 und Li4GeO4)

A New Oxogermanate: Li₈GeO₆ ? Li₈O[GeO₄] Transparent colourless single crystals of Li₈GeO₆(P6₃cm, a = 550.09(8), c = 1072.2(3) pm, Z = 2; 4-circle-diffractometer Siemens AED 2, MoKα; 326 I_o(hkl), R = 2.4%, R_w = 2.0%), have been prepared. As by-product we always got colourless isometric single crystals of Li₄GeO₄. For the first time we could grow single crystals of Li₈SiO₆ of suitable size and quality. Our structure refinement confirms the assumed structure model [2]: Li₈GeO₆ and Li₈SiO₆ are isotypic with Li₈CoO₆[3] (Li₈SiO₆: a = 542.43(8), c = 1062.6(2) pm, Z = 2; 4-circle-diffractometer Siemens AED 2, MoK_α; 306 I_o(hkl), R = 3.6%, R_w= 3.0%). The known crystal structure of Li₄GeO₄ [4] is confirmed and refined (Cmcm, a = 776.6(2), b = 735.7(3), c = 604.9(2) pm, Z = 4; 4-circle-diffractometer Siemens AED 2, MoKα, 298 I_o(hkl), R = 1.9%, R_w = 1.4%). The Madelung Part of Lattice Energy, MAPLE, and Effective coordination-Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated.     

Die Bestimmung kleiner Konzentrationen gelösten Sauerstoffes im Wasser

Zusammenfassung Die Anwendbarkeit des von uns vorgeschlagenen Verfahrens¹ für die Bestimmung von Sauerstoff im Mikromaßstab setzt geringfügige Veränderungen der Methode voraus (es wurde von dem Absaugen der überschüssigen Flüssigkeit über dem Niederschlag abgesehen und bei einigen Lösungen andere Konzentrationen verwendet), die aber das Prinzip der Methode nicht verändern.Bei visueller Indikation ist die Bestimmung von 0,5 mg O₂/l als untere Grenze mit einer Genauigkeit von 5% rel. möglich. Die Titration niedrigerer Sauerstoffkonzentrationen ist zwar möglich, aber mit grundsätzlich größeren Fehlern.Bei biamperometrischer oder potentiometrischer Indikation ist die Bestimmung von 10g O₂/l möglich. Für die Bestimmung geringerer Mengen sind diese elektronischen Methoden nicht mehr geeignet. Bei der Potentiometrie ist im Äquivalenzbereich eine kaum meßbare Potentialänderung wahrzunehmen, auch bei biamperometrischen Titrationen war es nicht möglich, eine brauchbare Kurve für die Bestimmung des Äquivalenzpunktes zu erzielen.Bei der Bestimmung des in Mikromengen gelösten Sauerstoffes sind die Vorteile der beschriebenen Semimikromethode gegenüber der jodometrischen Methode nachWinkler gewährleistet. Die Technik der Probenahme von Wasser mit sehr kleinen Sauerstoffkonzentrationen, die einen maßgebenden Einfluß auf die Genauigkeit der Bestimmung hat, bleibt die gleiche, wie bei anderen Methoden.

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Summary The applicability of the process¹ proposed by us for the determination of oxygen on the micro scale presupposes minor modifications of the method (the drawing off of the excess fluid over the precipitate was omitted and solutions of other concentrations employed for some solutions) but these did not alter the basic principle of the procedure.When visual indication is employed, it is possible to determine 0.5 mg O²/l as the lower limit with an accuracy of 5% (relative). The titration of lower oxygen concentrations is actually feasible but with fundamentally greater errors.When biamperometric or potentiometric indication is used, it is possible to determine as little as 10g O²/l. These electronic methods are no longer suitable for the determination of smaller amounts. In the case of potentiometry, a scarcely measurable potential difference was to be seen in the equivalence region, and likewise in the biamperometric titrations it was not possible to obtain a usable curve for the determination of the equivalence point.The advantages of the semimicro method described as compared with the iodometric method ofWinkler are shown definitely in the determination of the oxygen dissolved in micro quantities. The technique of taking samples of water that has a very small concentration of oxygen, which may have a decisive influence on the preciseness of the determination, is the same as in the other procedures.

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Résumé L'applicabilité du procédé¹ qui est proposé ici pour le dosage de l'oxygène à l'échelle micro suppose de légères modifications de la méthode (on n'a pas cherché à aspirer l'excès de liquide sur le précipité et on a utilisé d'autres concentrations pour quelques solutions); le principe en reste toutefois inchangé.Avec indication visuelle, le dosage de 0,5 mg O²/l comme limite inférieure avec une précision de 5% (rel.) est possible. Le titrage de concentrations plus faibles d'oxygène peut encore s'effectuer, mais avec de plus grandes erreurs de base.Avec indication biampérométrique ou potentiométrique, il est possible de doser 10g O²/l. Pour le dosage de quantités plus faibles, ces méthodes électroniques ne conviennent plus. Par potentiométrie, on peut déceler dans le domaine équivalent une modification à peine mesurable du potentiel, mais par titrages biampérométriques, il devient impossible d'atteindre une courbe utilisable pour la détermination du point équivalent.Dans le cas du dosage de l'oxygène dissous en microquantités, les avantages des semimicrométhodes qui sont décrites, par rapport à la méthode iodométrique deWinkler, sont certains. La technique du prélèvement de l'eau pour de très petites concentrations en oxygène, qui a une influence déterminante sur l'exactitude du dosage, reste la même que dans les autres méthodes.

     

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside and other glycosidic constituents from apple leaves

3,4-Dihydroxy-7,8-dihydro-beta-ionone 3-O-beta-D-glucopyranoside 1 has been isolated from a methanolic extract of apple (Malus domestica) leaves by XAD-2 adsorption chromatography and subsequent purification by high speed countercurrent chromatography (HSCCC) and HPLC. Under acidic conditions this glycoside gives rise to a number of volatile compounds including 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) 2, which is known as an off-flavor compound in wine. In the course of the study, six additional glycoconjugates were isolated from apple leaves, i.e. roseoside 3, 3-oxo-alpha-ionol beta-D-glucopyranoside 4, benzoic acid beta-D-glucose ester 5, kaempferol 3-O-rhamnoside 6, (+)-syringaresinol beta-D-glucopyranoside 7 and 4-hydroxy-5-(3'-methyl-2'-butenyl)-benzoic acid methylester 3-beta-D-glucopyranoside 8. The latter compound has been isolated for the first time in nature. In order to avoid the 'kerosene-off-flavor' caused by TDN, the methanolic extract has been subjected to yeast fermentation. This treatment reduced the amount of TDN formed and resulted in an improved flavor impression of the methanolic extract.     

Decay properties of isomeric states in radium isotopes close to N = 126

Isomeric states in ^210-215Ra have been populated by the decay of the compound nuclei ^216,220Ra produced in irradiations of ^204,208Pb with ¹²C at MeV. Published values for -ray energies and half-lives were confirmed for Ra. Our data for Ra agree with the -energies and the half-life measured at the RITU separator, University of Jyväskylä (Finland). Its decay pattern is complex. Two series of -rays of keV and keV were observed. A half-life of s was measured. The isomeric state is attributed to an 8 ⁺ state at E ^* = 2053.8keV. A previously unknown isomeric state was assigned to Ra. It has a half-life of ( ) and it decays by emission of -rays with energies of 396.1keV and 802.0keV. It is attributed to a 13/2 ⁺ state at E ^* = 1198.1 keV.PACS: 23.60. + e decay - 27.90. + b